I see other whey protein isolates that do claim to be lactose free – are they?

The term “Lactose-Free” as per the US and Canadian federal regulations is not permissible on any whey protein even if it contains less than 1% lactose. “Free” means “no detectable lactose” as per the regulations, and every whey isolate has some tiny amount of lactose. In essence, no whey isolate should be labelling their product as being Lactose-Free.